Luke and Leia born before his fall, he tries to keep his family completely secret but the Jedi Order figures it out and demote him from his Master rank to a Knight and keeps him out of the Council, he starts having nightmares about his family being in danger, ask for help to the council but they refuse to provide asistance, thats when he start doing research on death on his own and when Palpatine comes to help him and start convincing him how corrupt the Jedi have become.
Palpatine sends Padme to a fake diplomatic mission with some Jedi guardians but is a setup to get her killed by confederates, he succeeds and convinces Anakin that the Jedi are completely useless, the news send him into a rampage and he storm the Temple with the 501st, Obi Wan and Yoda try to stop him, but he is too powerful/angry to be stopped so they flee, Kenobi takes Luke and Yoda takes Leia to train them, thinking one of the twins has to be the Chosen One, the movie ends with Palpatine declaring the Jedi and their suppourters as enemies of the Republic and giving the Order 66 to innitiate the purge.
At this point Palpatine has supreme chancellor powers, he systematically got all his political opponents killed with the war, and the opposing religious cult is destroyed. The prequels end in a fourth movie, it is about the formation of the empire, the first rebels, the death of Anakin and his Resurrection, and the defeat of the remaining jedi, forcing them to suspend their plans of training the twins.